Compressed air switch with electrically controlled blasting of the switching gaps



June 25, 1963 A. EIDINGER 3,095,488

COMPRESSED AIR SWITCH WITH ELECTRICALLY CONTROLLED BLASTINQ OF THE SWITCHING GAPS Filed June 21, 1961 2 Sheets-Sheet l i E 7g N IN VEN TOR.

Aclofv ELcLLngef PQl JW Pan 2am A. EIDINGER 3,095,488 COMPRESSED AIR SWITCH WITH ELECTRICALLY CONTROLLED June 25, 1963 BLASTING OF THE SWITCHING GAPS 2 Sheets-Sheet 2 Filed June-21, 1961 INVENTOR. Adolf Eidinger United States Patent 3,095,488 COMPRESSED AIR SWITCH WITH ELECTRICALLY CONTROLLED BLASTING OF THE SWITCHING GAPS Adolf Eidinger, Nussbaumen, Switzerland, assignor to Brown, Boveri & Cie, Aktiengesellschaft, Mannheim, Germany, a joint-stock company Filed June 21, 1961, Ser. No. 118,686 Claims priority, application Germany June 29, 1960 3 Claims. (Cl. 200-448) The present invention relates to electrical switches and in particular to electrical switches of the type wherein the point of disconnection between the switch contacts is blast ed with compressed air in order to aid in extinction of the arc. Compressed air switches usually comprise one or a plurality of sets of relatively movable contacts electrically connected in series. One contact of each set is usually constructed in the form of a nozzle contact and the other contact is usually constructed as a pin contact which engages the end of the nozzle contact and closes off the compressed air passageway through the latter. One contact is fixed in position and the other is arranged for movement away from the fixed contact. Disengagement between the pin and nozzle contacts takes place in dependence upon the current flowing through the switch contacts by electromagnetic or elect-rodynamic produced forces, and compressed air taken from a suitable source of supply is blown onto the gap between the contacts as they separate, the compressed air entering the nozzle of the nozzle contact member and flowing through the latter and thence through an outlet valve in the switch assembly. Flow of the compressed air into the gap between the pin and nozzle contacts to quench the arc is usually maintained until the current has subsided to a predetermined value different from zero, and preferably adjustable.

The invention is directed to a further and advantageous development of a compressed air switch of the type described wherein a very simple means, actuated in dependence upon the amplitude of the current flowing through the switch contacts is provided for blocking the movable one of the switch contact members in a fixed, are quenching position spaced closely from the stationary contact but only in the event the current attains a predetermined amplitude or higher and wherein such contact holding means is released at lower current amplitudes to permit the movable switch contact member to move further to its full disengaged position. If the switch current does not attain the predetermined amplitude, the blocking device remains inoperative.

In particular, the blocking device is comprised of a ring of ferromagnetic material which is arranged in a fixed position concentrically about and spaced radially from the movable contact member, for example, the nozzle contact member. The ferromagnetic ring includes at least one radial gap therein, and an armature movable into said gap and which is adapted to engage and block further movement of the movable contact member. The ferromagnetic ring in combination with the current flow through the nozzle contact member thus forms an electromagnet, the electromagnetic force acting upon the armature to attract the same into the gap being dependent upon the magnitude of the magnetic flux flowing through the ring, and the magnetic flux in turn being dependent upon the magnitude of the current flowing through the nozzle contact member. Thus, the attractive force on the armature which determines whether it will, or will not, move into a contact blocking position is made dependent upon the magnitude of the current flowing through the switch contacts. The arrangement is such that the armature is attracted to its blocking position when and for so long as the switch current exceeds a predetermined magnitude, and releases when the current drops below this predetermined magnitude.

In accordance with one embodiment of the invention to be described, the armature element of the electromagnet is adapted when attracted into the radial gap in the ice ferromagnetic ring to engage a stop provided on the sur face of the movable contact and thus block further movement thereof, the stop being movable through the gap in the ring when the armature is released so as to permit the movable contact member to resume movement to its final disengaged position.

In accordance with another embodiment of the invention, also to be described, the armature element of the electromagnet is adapted when attracted into the radial gap in the ferromagnetic ring to enter a recess provided in the wall of the movable contact and thus block further movement thereof in either direction.

The armature element of the electromagnet can, if desired, -be constructed partly from soft iron and partly from laminated alloy sheets or a core wound from a single alloy strip. In this manner, one obtains two, phase-displaced, armature tractive force characteristics, one for the soft iron part and one for the laminated part, which overlap each other and thus give a resultant tractive force at which oscillation which otherwise might be expected, no longer appears. The heating of the electromagnet is of no consequence since it responds only for short periods, if indeed at all.

It is a further advantage of the invention that the electromagnet consisting of the ferromagnetic ring and armature can be calibrated completely independent of the remaining switch structure. Since it is important merely that the armature element of the electromagnet respond at high currents which the switch can no longer control, in order to block further movement of the movable contact so that the nozzle and pin contacts remain in a desired closely spaced and are quenching position, there are no demanding requirements to be made with respect to the design and calibration of the electromagnet. Thus, a simple ferromagnetic ring with an armature which responds only with very high currents is suflicient to attain the result desired.

device for blocking movement of the switch contact can be readily and easily applied to compressed air switches already in use. Since these switches must be inspected at regular intervals, for example, after the switch has functioned to switch off high magnitude short-circuit currents,

the very simple ferromagnetic ring and its associated armature together with the cooperative stop member on the movable contact can then be installed.

Additional valve devices which would require extensive changes in construction of the switch and at very great exv pense, are not necessary here. Through the blocking of the movable contact in the quenching position as a result of the excitation of the electromagnet in the case of high short-circuit currents, the compressed air outlet valves associated with the switches being considered remain automatically opened, and only when the current has subsided does the electromagnet release the movable contact so that the latter can then resume its movement to the full disconnected position from the stationary contact at which time the outlet valves close.

The foregoing as well as other objects and advantages inherent in the invention will become more apparent from the following detailed description of certain embodiments thereof, in conjunction with the attached drawings. In these drawings,

FIG. 1 is a view inlongitudinal central section through the axis of the contact members of an electrical switch of the compressed air type showing one embodiment of the invention, the remainder of the switch structure including the hollow insulator within which the contact members are located, the compressed air tank and associated control valve structure, the outlet valve through which compressed air is discharged after passing through the nozzle contact, and the means by which a separating movement of the contacts is initiated being omitted since these switch components are conventional and not considered essential to a disclosure of the inventive concept itself;

FIG. 2 is a transverse sectional view taken on line 2-2 of FIG. 1 looking towards the left;

FIG. 3 is a view similar to FIG. 1 showing a second embodiment of the invention; and

FIG. 4 is a transverse sectional View taken on line 44 of FIG. 3.

With reference now to FIGS. 1 and 2, the compressed air switch structure is seen to include two contact members 1 and 2 which are arranged to be moved relative to each other to effect their engagement and disengagement. One of the contact members such as contact member 1 is constructed as a nozzle contact member and also as the movable contact member. It is characterized by the cylindrical tube of electrically conductive metallic material and includes an entry nozzle 1a which constitutes a seat for the rounded end 2a of the other, stationary pin contact member 2 when the two contact members are engaged. Nozzle 1a also constitute-s a point of entry for compressed air as the contact members are disengaged, the compressed air serving to blast and quench the are formed in the gap between the contact members. In accordance with the invention, an electromagnet is associated with the movable one of the contact members to hold the latter in a quenching position close to but separated from the stationary contact member. This electromagnet is comprised of a stationary ring 3 of ferromagnetic material which is placed concentrically about and spaced radially from the nozzle contact member 1 so as to allow the latter to move axially through the same. At least one radial gap 3a is provided in the ring 3 and the Wall portions defining this gap are provided with an external shoulder 3b forming a seat for an armature 4 which is attra-ctable into the gap so as to close the same whenever a sufficient magnetic attracting force is developed in the ring 3. Armature 4 is mounted at the outer end of a cantilever spring 5 which functions to maintain the armature in a position exteriorly of the gap, the position shown in full lines, unless an attractive force of sufiicient magnitude is built up to overcome the inherent biasing force of the spring. The armature member 4 may be constructed entirely from. soft iron, as illustrated, or it may be constructed partly from soft iron and partly from laminated alloy sheets or a core wound from a single alloy strip.

Fixed into the wall of the hollow contact member 1 and extending radially outward therefrom is a stop member 6 having a width such as will permit it to pass freely through the gap 3a in ring 3 as the contact member 1 is shifted to the right to disengage it from the pin contact member 1 unless it is blocked by armature 4. Ring 3 together with the current conductor established by the contact member 1 form an electromagnet, and the magnetic flux induced to flow circumferentially through the ring depends upon the magnitude of the current flowing through the switch contact member 1. If a Very high current such as one of short-circuit proportion flows through the contact member 1 the flux in ring 3 will be sufficient to attract armature 4 and draw it sufficiently down into the gap 3a, the position shown in broken lines, so as to engage the stop 6 when the nozzle contact member 1 reaches the position of the armature. The nozzle contact member 1 will thus be blocked against 'further opening movement toward the right and is thus held in the quenching position closely spaced from the pin contact member 2. After the current flowing through the nozzle contact member 1 decreases below the predetermined value at which the armature 4 becomes attracted into blocking contact with the stop member 6, the armature 4 moves back into the position indicated in the drawing, thus unblocking the stop member 6 and permitting the nozzle contact member 1 to continue its movement toward the right and attain its final switched-out position. The exhaust valve, not shown, through which is exhausted the compressed air passing through the nozzle contact member, remains open as long as the nozzle contact member is held in the blocked, quenching position.

In the embodiment illustrated in FIGS. 1 and 2 the ferromagnetic ring 3 is provided with two gaps 3a in diametrally opposed relation, two armatures 4 and two of the stop members 6 also diametrally situated. This is done to attain a symmetrical balance for the blocking forces applied to the nozzle contact member 1 but it is obvious that a single gap, armature and stop member organization would be sufficient to attain the desired result.

FIGS. 3 and 4 illustrate a second embodiment of the invention wherein the one or more radially extending stop members 6 are replaced with equivalent stops in the form of recesses 7 established in the Wall of the nozzle contact member 1. This embodiment of the invention operates in tinuing high magnitude, short-circuit current the air pres sure in the quenching chamber returns, the nozzle contact member 1' cannot slide back under the pressure of the spring which Works upon it but which is not illustrated in the drawing. In the embodiment of FIGS. 3 and 4, the armatures 4 can be attached to cantilever springs 5 arranged parallel With the axis or they can be attached to radially acting tension springs.

In conclusion, while preferred embodiments of the invention have been described and illustrated, it will be evident that various minor modifications in the construction and arrangement of component parts may be made without, however, departing from the spirit and scope of the invention as defined in the appended claims.

Also, While the inventive concept has been illustrated in embodiments wherein the nozzle contact member is the one which is made movable, the pin contact member being stationary, it will be evident that the same contact movement blocking arrangement can be applied to the pin contact member in a switch construction wherein the pin contact member is moved and the nozzle contact member remains stationary.

I claim:

1. In a compressed air electrical switch the combination comprising a pair of contact members, one of said contact members being a pin contact and the other of said contact members being a nozzle contact, said contact members being relatively movable towards and away from each other to effect engagement and disengagement respectively, a ring of ferromagnetic material surrounding said movable contact member and spaced therefrom to permit said movable contact member to be displaced longitudinally of itself, said ferromagnetic ring being provided with at least one gap extending radially, and an armature member magnetically attractable into said gap only when the current through said movable contact member reaches a predetermined maximum amplitude, said armature member when attracted into said gap being cooperative with means provided on said movable contact member to block further movement thereof in the contact disengaging direction and thereby hold the nozzle of said movable contact member in a spaced quenching position from the end of said pin contact member.

2. A compressed air electrical switch as defined in claim 1 wherein said means provided on said movable contact member which cooperate with said armature member to block further movement of said movable contact member is constituted by a stop member aligned with said gap in said ferromagnetic ring and which engages said armature member.

3. A compressed air electrical switch as defined in claim 1 wherein said means provided on said movable contact member which cooperate with said armature member to 'block further movement of said movable contact member is constituted by a recess in the Wall thereof aligned with said gap in said ferromagnetic ring and into which said armature member is attracted.

No references cited. 

1. IN A COMPRESSED AIR ELECTRICAL SWITCH THE COMBINATION COMPRISING A PAIR OF CONTACT MEMBERS, ONE OF SAID CONTACT MEMBERS BEING A PIN CONTACT AND THE OTHER OF SAID CONTACT MEMBERS BEING A NOZZLE CONTACT, SAID CONTACT MEMBERS BEING RELATIVELY MOVABLE TOWARDS AND AWAY FROM EACH OTHER TO EFFECT ENGAGEMENT AND DISENGAGEMENT RESPECTIVELY, A RING OF FERROMAGNETIC MATERIAL SURROUNDING SAID MOVABLE CONTACT MEMBER AND SPACED THEREFROM TO PERMIT SAID MOVABLE CONTCT MEMBER TO BE DISPLACED LONGITUDINALLY OF ITSELF, SAID FERROMAGNETIC RING BEING PROVIDED WITH AT LEAST ONE GAP EXTENDING RADIALLY, AND AN ARMATURE MEMBER MAGNETICALLY ATTRACTABLE INTO SAID GAP ONLY WHEN THE CURRENT THROUGH SAID MOVABLE CONTACT MEMBER REACHES A PREDETERMINED MAXIMUM AMPLITUDE, SAID ARMATURE MEMBER WHEN ATTRACTED INTO SAID GAP BEING COOPERATIVE WITH MEANS PROVIDED ON SAID MOVABLE CONTACT MEMBER TO BLOCK FURTHER MOVEMENT THEREOF IN THE CONTACT DISENGAGING DIRECTION AND THEREBY HOLD THE NOZZLE OF SAID MOVABLE CONTACT MEMBER IN A SPACED QUENCHING POSITION FROM THE END OF SAID PIN CONTACT MEMBER. 